The present invention relates to compositions and methods for preparing teeth having cavities for restoration with a restorative material. A preferred composition may be characterized as a dental cavity varnish.
Cavity varnishes are commonly used in dentistry as adjuncts to restorative materials. Their role, in general, is to provide better pulp protection by sealing dental tubules thus preventing penetration of micro-organisms, reducing sensitivity to temperature changes and preventing penetration of potentially toxic substances from restorative materials that may damage or kill the pulp. The beneficial effects of cavity varnishes in preventing the occurrence of secondary caries, in elimination of post-operative tooth sensitivity and preservation of pulp vitality have been clinically well documented.
In their function, cavity varnishes are related to cavity liners (or bases) that are used for covering of the floor of the cavity in the deep restorations providing mechanical as well as anti-poison protection for the pulp and sometimes stimulating secondary dentine formation. While cavity liners are, by application requirements, of rather thick consistency and able to cure forming a relatively strong solid mass, cavity varnishes must be in the form of low to medium viscosity liquids that can be painted over the cavity wall. They should wet the dentine tissue well and leave, after drying, an adhesive film that seals the exposed dental tubules well.
Calcium hydroxide containing formulations are preferred as cavity liners for their compatability with all types of restorative materials, ability to stimulate secondary dentine formation and excellent compatability with the pulp. Unfortunately, commonly known calcium hydroxide type materials are generally unsuitable for use as cavity varnishes because of their consistency, inadequate mechanical properties when cured in a thin film, solubility in oral fluids and poor adhesion to dentine. Zinc oxide/eugenol type compositions, also commonly used as cavity liners, have the same disadvantages as calcium hydroxide formulations when it comes to consistency and mechanical properties and adhesion to dentine. In addition, they are incompatible with methacrylate resin based restorative materials, inhibiting their cure. This last characteristic is of special importance since so-called composite restoratives that use methacrylate monomers as binders are becoming the most frequently and universally used restorative materials.
Cavity varnishes, presently in use in dentistry, consist principally of solutions of solid materials in low boiling solvents. Most commonly used are solutions of natural gums such as copal or rosin in acetone or chloroform. They form solid films not through a chemical reaction but as a result of evaporation of the solvent. Adhesion to the dentine and sealing properties of these materials have been found adequate and, if proper caution is exercised, no toxic effect to the pulp may be expected from either the cured resin or the solvent.
The main limitation of natural gum-based cavity varnishes is their incompatability with methacrylate resin type restoratives. This limitation is considered very essential since methacrylate resins may leak toxic substances that may cause serious damage to the pulp. It is especially important, therefore, to seal dental tubules in order to prevent the penetration of toxic materials. The use of a liner under methacrylate resin based restoration is also desirable because these materials do not adhere to dentine and they shrink during cure, leaving the dentine unprotected. Marginal sealing is not always possible or sufficient to prevent secondary decays resulting from bacteria attack, tooth sensitivity or damage to the pulp caused by chemical substances present in the oral environment. Besides compatability with commonly used restorative materials and ability to adhere to dentine, the ideal varnish should meet the following requirements:
it should not be toxic or irritating. PA1 it should cure or dry fast at body temperature or slightly higher. PA1 it should be chemically resistant to the oral environment. PA1 it should be easy to apply, preferably with a paint-on technique.
Until now, no dental varnish was available that would satisfy all these requirements.